This application, and the innovations and related subject matter disclosed herein, (collectively referred to as the “disclosure”) generally concern vented acoustic transducers and related methods and systems. Some configurations of disclosed acoustic transducers combine or integrate attributes and structure conventionally found distributed between or among separate system components or modules. Such configurations can eliminate one or more conventional components while retaining one or more functions conventionally provided by the eliminated component. More particularly but not exclusively, acoustic transducers having a vented acoustic diaphragm are disclosed. Examples of acoustic-transducers include loudspeaker transducers, and microphone transducers. Both can have a barometrically-vented diaphragm and are but specific examples of disclosed acoustic transducers used herein to facilitate description of innovative principles that can be applied among a variety of transducer embodiments, as will be appreciated by those of ordinary skill in the art following a careful review of this disclosure. As well, this disclosure describes examples of systems and methods pertaining to innovative acoustic transducers.
In general, an acoustic signal constitutes a vibration that propagates through a carrier medium, such as, for example, a gas, a liquid, or a solid. An acoustic transducer, in turn, is a device configured to convert an incoming acoustic signal to another form of signal (e.g., an electrical signal), or vice-versa. Thus, an acoustic transducer in the form of a loudspeaker can convert an incoming signal (e.g., an electro-magnetic signal) to an emitted acoustic signal, while an acoustic transducer in the form of a microphone can be configured to convert an incoming acoustic signal to another form (e.g., an electro-magnetic signal).
A loudspeaker can emit an acoustic signal in a carrier medium by vibrating or moving an acoustic diaphragm to induce, or otherwise inducing, a pressure variation or other vibration in the carrier medium. For example, an electromagnetic loudspeaker arranged as a direct radiator can induce a time-varying magnetic flux in a coil (e.g., a wire formed of copper clad aluminum wrapped around, for example, a bobbin) by passing a corresponding time-varying current through the coil (sometimes referred to in the art as a “voice coil”). The coil can be positioned adjacent one or more magnets (e.g., a permanent magnet having a fixed, or an electromagnet having a variable, magnetic field). A resultant force as between the magnetic flux emanated from the coil and the magnetic field(s) of the one or more magnets can urge the coil into motion, preferably a pistonic motion in some embodiments.
The coil, in turn, can be directly or indirectly coupled with an acoustic diaphragm configured to induce a pressure variation in a surrounding carrier medium as the diaphragm moves in correspondence with the, e.g., pistonic, movement of the coil. The diaphragm can be rigid, or semi-rigid, and often is light weight to reduce inertial effects and allow the acoustic diaphragm to vibrate or otherwise induce a pressure variation or other vibration in a surrounding or adjacent carrier medium. The coil and/or the bobbin can provide a measure of structural stability to the membrane, as to maintain predominately pistonic movement in the diaphragm.
Further, the diaphragm can be suspended from or otherwise movably supported by a frame. A suitable suspension system generally provides a restoring force to the diaphragm to maintain the coil in a desired position and/or orientation. The suspension allows for controlled axial (e.g., pistonic) motion, while largely preventing lateral motion or tilting that could cause the coil to strike another motor component, or otherwise induce distortion or mechanical inefficiency leading to degraded performance of the transducer.
Conversely, despite having a similar physical arrangement compared to the just-described loudspeaker, a microphone transducer can be configured to convert an incoming acoustic signal to, for example, an electrical signal. For example, an acoustic diaphragm of a microphone transducer can vibrate, move, or otherwise respond to a pressure variation received through a surrounding or adjacent carrier medium. Movement of the coil through the magnetic field can induce a corresponding electrical current through the coil. Accordingly, a time-varying movement of the coil can induce a corresponding time-varying electrical current through the coil. Such a time-varying electrical current can be converted to a machine-readable form (e.g., digitized).
Regardless of their precise configuration, performance or operation of such acoustic transducers can be negatively affected, and such transducers can even be rendered inoperable, if the mode of emitting or receiving an acoustic signal is inhibited or prevented. For example, some use conditions can apply a load to a conventional acoustic diaphragm sufficient to inhibit or prevent movement or vibration of the diaphragm. More specifically, a large pressure gradient applied across a conventional acoustic diaphragm can bias the diaphragm to an outermost (or innermost) position of displacement. As another example, a contaminant can prevent or inhibit movement of an acoustic diaphragm past a given position within the diaphragm's typical range-of-displacement. In either event, operation of the acoustic transducer, whether configured as a loudspeaker or a microphone, can be negatively affected, or the transducer can be altogether rendered inoperable. Examples of negative effects include acoustic distortion or lower-than-normal amplitude (e.g., emitted or detected loudness). Such performance degradation can continue until the pressure gradient is equalized, or the contaminant is removed.
Barometrically venting an acoustic enclosure or module has been proposed to alleviate or to eliminate such pressure-induced performance degradation. As but one example, U.S. Pat. No. 9,363,587, which is hereby incorporated by reference as fully as if reproduced herein in its entirety, for all purposes, disclosed a pressure vent for speaker or microphone modules.
Moreover, acoustic transducers, as well as modules and systems incorporating such transducers, continue to be made smaller. However, it may be desirable in some instances for an acoustic transducer, and more particularly for an acoustic diaphragm, to maintain a physical size above a lower threshold size to achieve desired acoustic properties and/or functional attributes.
Thus, a need remains for acoustic transducers suitable for use across a wide range of environmental (or ambient) pressures. As well, a need remains for acoustic transducers configured to meet or to exceed desired acoustic performance targets. And, a need exists for such acoustic transducers to be configured for use in a compact physical environment.